From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CCB05C4742C for ; Fri, 13 Nov 2020 21:44:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 937AB221EB for ; Fri, 13 Nov 2020 21:44:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="Gr4rBDYm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726302AbgKMVoY (ORCPT ); Fri, 13 Nov 2020 16:44:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726196AbgKMVoV (ORCPT ); Fri, 13 Nov 2020 16:44:21 -0500 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DADACC0617A6 for ; Fri, 13 Nov 2020 13:44:20 -0800 (PST) Received: by mail-pf1-x443.google.com with SMTP id y7so8708668pfq.11 for ; Fri, 13 Nov 2020 13:44:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=jBsaCjpf4fscNVFcDQCUrtRqqAxNkOKkyOP/x0Yudbc=; b=Gr4rBDYmhAURHlZdqniWVzqgh0UPjNiLW5C7SZjZo6+m3uzG+myWFHJpukpFg1hZGC DBkt8YetnAu+1tlaW8pONEoyptygCmDHHeVcTmvuSXrG1x4GM5XEn1+KXtNDO97Erp7v lEAfkw91U9TIceWHaRlW3v34f+6VCYbZiv6f7N/5xa7ZSGfVidyR0Pe2zOcxkIUOxkGp yi6Xs18gY6D9XAcMEUKilBgjkfxljkAHUTDrFsRIzMlqWalwJin6OgKQbED41DTnQ1xX zjlLu6y2PtnP4QWpF9XtCmNYTJE2xHINHxT8ilUlMg+J8JPUQaWxf9EFpMRHBKz9HmUz gEGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=jBsaCjpf4fscNVFcDQCUrtRqqAxNkOKkyOP/x0Yudbc=; b=GGwqOPejAL4JgA2F4gN6ZRLSDkA+yEaZzwP/qb4/DBhBET6T6Yrl89ilGZ2+Vcq54K 7hW/7a/ECFv54oH1smPKZDrSbe42AOrTSED+ikhO5wLlifZkv/CQPNsc5CI6xU7NHV9f AcJ7683kJBP7iihQ9oHPotT/LLKqnyOHB0hwBrfZwZDWuRJ50/8Ft2bvA8KBIevdBkhQ RLdNwwkestQINDVRBZWTzyLTDDeWh+IWRXmtZwcBF218lojrmFDKEb2lrcWVH6Bvthjc waIsjrdxtIzyZqStCrUm2V9PKDPgW1e292wp5AADeuoXaPjB+ueGdjqO4Izk6QdEgexx Mo9w== X-Gm-Message-State: AOAM533czH+7WOYgajWnPBBBi/BZEuKacPO9/YTaey+RDrocNUDo2UOp yOafAXCUUKTNjYMRxd/Ssm8ue6lFsLBVPA== X-Google-Smtp-Source: ABdhPJzCyynwsxcziuAqEG55g3gd7FIeqfF7PAuUNlkzvPcZ1Wg+ErlM+sNy+2DMiwCJ9g1Hh4W94Q== X-Received: by 2002:aa7:959d:0:b029:18b:5b6a:2553 with SMTP id z29-20020aa7959d0000b029018b5b6a2553mr3649463pfj.47.1605303860256; Fri, 13 Nov 2020 13:44:20 -0800 (PST) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id i29sm9621029pgb.10.2020.11.13.13.44.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Nov 2020 13:44:19 -0800 (PST) Subject: Re: [PATCH] iosched: Add i10 I/O Scheduler To: Sagi Grimberg , Rachit Agarwal , Christoph Hellwig Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Keith Busch , Ming Lei , Jaehyun Hwang , Qizhe Cai , Midhul Vuppalapati , Rachit Agarwal , Sagi Grimberg , Rachit Agarwal References: <20201112140752.1554-1-rach4x0r@gmail.com> <5a954c4e-aa84-834d-7d04-0ce3545d45c9@kernel.dk> <10993ce4-7048-a369-ea44-adf445acfca7@grimberg.me> From: Jens Axboe Message-ID: <26a1cd20-6b25-eaa6-7ab6-ba7f5afaf6dd@kernel.dk> Date: Fri, 13 Nov 2020 14:44:17 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/13/20 2:36 PM, Sagi Grimberg wrote: > >>> But if you think this has a better home, I'm assuming that the guys >>> will be open to that. >> >> Also see the reply from Ming. It's a balancing act - don't want to add >> extra overhead to the core, but also don't want to carry an extra >> scheduler if the main change is really just variable dispatch batching. >> And since we already have a notion of that, seems worthwhile to explore >> that venue. > > I agree, > > The main difference is that this balancing is not driven from device > resource pressure, but rather from an assumption of device specific > optimization (and also with a specific optimization target), hence a > scheduler a user would need to opt-in seemed like a good compromise. > > But maybe Ming has some good ideas on a different way to add it.. So here's another case - virtualized nvme. The commit overhead is suitably large there that performance suffers quite a bit, similarly to your remote storage case. If we had suitable logic in the core, then we could easily propagate this knowledge when setting up the queue. Then it could happen automatically, without needing a configuration to switch to a specific scheduler. -- Jens Axboe